The present invention relates to the drive train of a vegetation mower, and in particular to the drive train of a mower utilizing a single pulley belt in conjunction with dual mechanical transmissions.
A major component of vegetation mowers is the drive train, which transfers power from the engine to the ground engaging wheels. A typical drive train includes a single transmission. In more recent times, with the advent of using drive wheels to steer the mower, two transmissions operatively connected one to each of the drive wheels of the mower is common. Each transmission is separately controlled so that the drive wheels may be driven at different speeds. One transmission may selectively be disengaged allowing that corresponding wheel to stop rotating in order to limit damage to the turf during tight turns. In either case, driving the wheels at different speeds effectively steers the vehicle.
One method of driving the wheels of a mower at different speeds is disclosed in U.S. Pat. No. RE 34,057. This patent discloses a vehicle having two hydrostatic drive transmissions providing power input to a corresponding pair of left and right driving wheels. This patent further discloses a steering mechanism and an accelerator mechanism. The accelerator mechanism provides input to the two transmissions.
U.S. Pat. No. 5,816,034 also discloses a belt drive system for a grounds care device using two hydrostatic transmission power units. This patent allows for two identical hydrostatic transmission units to be incorporated due to an asymmetrical design of the drive train.
A second method of driving the wheels of a mower at different speeds is disclosed in U.S. Pat. No. 3,999,444. This patent discloses two transmissions having instant reversing capability and vehicle steerage capability. A plurality of pulley plates and pulley belts are used to provide input to each of the transmissions.
Although hydrostatic transmissions work well for their intended purpose, one disadvantage with them is their cost. While the hydrostatic drives provide precise control over the drive wheels, they also substantially increase the cost of manufacturing such a drive train. It is also often necessary to add to the hydrostatic drive, a gear reduction mechanism to provide the required rotational speed to the drive wheels. What is needed is a drive train that provides separate drive wheel control without the use of expensive hydrostatic transmissions.
A disadvantage with known mechanical transmissions, as described above, is that the drive train requires a plurality of pulleys and belts to provide input into the transmissions. The plurality of components increases manufacturing costs and maintenance costs, since the pulleys and belts are interconnected and must be adjusted over the course of normal usage. Additionally, replacement or repair costs are also increased; as there are increased components that are affected by wear.
It would therefore be advantageous to provide a drive train for use on a vegetation mower that would reduce the cost of manufacturing and maintaining the vegetation mower, while providing the capability of driving the wheels at different speeds. It would also be advantageous to provide a simplified drive train using cost effective mechanical transmissions and a single pulley belt.
It is therefore an object of the present invention to provide vegetation mower having dual mechanical transmissions driven by a single belt that drive the ground engaging wheels at different speeds.
It is also an object of the present invention to reduce the cost of manufacturing a vegetation mower that incorporates a dual transmission drive train.
It is still another object of the present invention to reduce the cost and complexity of maintenance for a vegetation mower that incorporates a dual transmission drive train.
It is yet another object of the present invention to provide dual mechanical transmissions with variable input pulleys.
According to the present invention, a vegetation mower is provided having dual mechanical transmissions operatively attached one to each of two ground engaging wheels. Each of the transmission drives have an input shaft whereon is mounted a driven pulley. Each of the driven pulleys is communicated to a driving pulley, which is operatively connected to an output of the engine via a single pulley belt. An idler pulley maintains operative tension of the pulley belt during normal operation. The outputs of the transmissions are connected one to each of the drive wheel axles. The transmissions are operated by selectively engaging a clutching means. In one embodiment, the driven pulleys are variable pulleys whereby the pulley belt engages a conical surface of the pulley at any point within an affective operating region of the conical surface. In this manner, input to the transmission may be selectively varied without affecting the input to the other transmission.
Still other benefits and advantages of the invention will become apparent to those skilled in the art to which it pertains upon a reading and understanding of the following detailed specification.